1. Field of the Invention
The present invention relates to an automobile headlight, and more particularly to a composition of the automobile headlight having a single fixed light source, a reflector, a fixed shade and a movable shade, characterized in that the fixed shade and the movable shade control light emitted from the light source to the reflector such that a light distribution of the headlight changes depending on whether the automobile is traveling straight ahead or by-passing another vehicle.
2. Discussion of the Related Art
FIG. 7 illustrates a conventional automobile headlight 90 comprising a light source 91, a reflector 92, a fixed shade 93, a movable shade 94 capable of taking a by-passing position or a traveling position depending on whether an automobile is traveling straight ahead or by-passing another vehicle, and a driving unit 95 to change a position of the movable shade 94. The reflector 92 further comprises a by-passing reflecting portion 92a, which reflects light emitted from the light source 91 when the movable shade 94 is in a by-passing position, having a rotated parabolic surface with a focus f1 positioned backward of the light source 91 in an illuminating direction, and a traveling reflecting portion 92b, which reflects light emitted from the light source 91 when the movable shade 94 is in a traveling position, and having a rotated parabolic surface with a focus f2 on the light source 91. The traveling reflecting portion 92b is around an upper end of the reflector 92 when the headlight 90 is disposed in the automobile. The fixed shade 93 prohibits light emitted from the light source 91 directly into an illuminating direction, and also prohibits emitted light toward a portion of the reflector 92. Reflected light at the portion of the reflector 92 forms unnecessary light distribution patterns. The movable shade 94 is moved by a driving unit 95 like a solenoid, and takes a traveling position P or by-passing position Q depending on whether the automobile is traveling straight ahead or passing by another vehicle. When the movable shade 94 is in the Q position, the movable shade 94 prohibits light emitted from the light source 91 towards the traveling reflecting portion 92b, thereby providing a light distribution pattern S for by-passing comprising light emitted downward from the reflecting portion 92a as depicted in FIG. 8. When the movable shade 94 is in the P position, as depicted by broken lines in FIG. 7, the movable shade 94 partially covers the fixed shade 93. Light emitted from the light source 91 thus reaches the traveling reflecting portion 92b, thereby providing a light distribution pattern M for traveling straight ahead, which comprises a light distribution pattern M2 that is light reflected on the traveling reflecting portion 92b toward the horizontal far front of the automobile headlight 90, and also provides the light distribution pattern S for by-passing, which comprises downward light reflected on the by-passing reflecting portion 92a. The light distribution pattern M is a combination of the light distribution patterns M2 and S.
The conventional automobile headlight 90 has the following problems. Even after a light distribution pattern is changed from by-passing to traveling straight ahead, long distance visibility does not significantly improve because the driver's pupils contract when sensing the downward bright area close to the automobile, which consequently decreases the driver's luminosity. A characteristic of the light distribution pattern S for by-passing, i.e. illuminating a downward bright area in a relatively close range to the automobile, still remains even after the light distribution is changed from the pattern S for by-passing to the pattern M for traveling straight ahead, because the light distribution pattern M for traveling straight ahead is formed by adding the light distribution pattern M2, which comprises light emitted in a horizontal front direction, to the light distribution pattern S comprising light emitted downward in a close range to the automobile.